Scroll type machines are becoming more and more popular for use as compressors in both refrigeration as well as air conditioning applications due primarily to their capability for extremely efficient operation. Generally, these machines incorporate a pair of intermeshed spiral wraps, one of which is caused to orbit relative to the other so as to define one or more moving chambers which progressively decrease in size as they travel from an outer suction port toward a center discharge port. An electric motor is provided which operates to drive the orbiting scroll member via a suitable drive shaft. Because scroll compressors depend upon a seal created between opposed flank surfaces of the wraps to define successive chambers for compression, suction and discharge valves are generally not required. However, when such compressors are shut down, either intentionally as a result of the demand being satisfied or unintentionally as a result of a power interruption, there is a strong tendency for backflow of compressed gas from the system in combination with high pressure gas contained in the chambers and/or discharge muffler to effect a reverse orbital movement of the orbiting scroll member and associated drive shaft. This reverse movement often generates objectionable noise or rumble. Further, in machines employing a single phase drive motor, it is possible for the compressor to begin running in the reverse direction should a moment a ry power failure be experienced.
In order to limit such reverse rotation, prior art scroll compressors have incorporated ball type check valves at the point of connection between the outer shell and the discharge line. While such ball type check valves have been effective to limit back flow of compressed refrigerant, they have demonstrated a tendency to vibrate or chatter under certain flow conditions thus presenting a further source of objectionable noise. Also, in severe situations, the chattering may result in damage or destruction of the ball stop and/or seat. Additionally, the occasional discharge of liquid through such ball type check valves further increases the possibility of damage thereto.
Other prior art scroll compressors incorporate disc type check valve in the outlet from the outer shell which effectively prevents return flow of compressed gas from the refrigeration system and hence limits reverse orbital movement of the orbiting scroll member. Because reverse orbital movement is thus limited, the possibility of objectionable noise being generated thereby upon shut down of the compressor is greatly reduced. The disc type discharge valve does not require any biasing means but rather operates to create a pressure differential thereacross which moves the disc between seated and unseated positions. The disc type discharge valve provides an inexpensive, easily installed means to effectively resist reverse movement of the orbiting scroll. Further, because a relatively large stop surface area is provided extending around the periphery of the valve member, the possibility of damage from discharge of liquid therethrough is greatly reduced.
While the above described disc valves have performed satisfactorily, the manufacture of the individual components of the disc type check valve required the machining of a housing and the machining or powder metal forming of one or more of the valve components. Both of these forming operations are relatively expensive leading to an increase in the manufacturing costs. The present invention overcomes the problems associated with the relatively expensive forming operations by providing a disc type check valve assembly where all of the components of the check valve assembly are manufactured by using a relatively lower cost stamping process or a powdered metal process. In one embodiment, one of the valve members is integral with the shell of the compressor.
Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.